Automatics only have 2 pedals, accelerator and brake and they are fairly close together. I have 3 american cars, all automatic. I have use in both feet but on occasion (long journeys) I suffer from cramp in my right leg, so switch legs. It may be possible for the pedals to be moved across a little to suit your needs. A guy at work has a false leg and he drives automatics.
A Vauxhall Corsa is on the motability list & is one of the more economical automatics I have found...having a similar problem to yours.
They can swap the pedals around to suit your working foot. They also give grants if you need adaptations.